1. Technical Field
Embodiments of the present invention relate to an apparatus and method for determining the location of a terminal and, more particularly, to an apparatus and method for determining the location of a terminal that simultaneously receives at least two pieces of location information in visible light communication (VLC) using LED illumination lights that transmit location information.
2. Description of the Related Art
Visible light is light having a wavelength in the range visible to the human eye among electromagnetic waves. The wavelength ranges from 380 to 780 nm. In visible light, a variation in characteristics attributable to a difference in wavelength is exhibited in the form of color, and the wavelength decreases across the spectrum from red to violet. Light having a wavelength longer than that of red color is referred to as infrared light, and light having a wavelength shorter than that of violet is referred to as ultraviolet light. In the case of monochromatic light, 700˜610 nm corresponds to red, 610˜590 nm corresponds to orange, 590˜570 nm corresponds to yellow, 570˜500 nm corresponds to green, 500˜450 nm corresponds to blue, and 450˜400 nm corresponds to violet. A variety of colors can be represented by mixing colors having these wavelengths.
Visible light is visible to humans, unlike infrared light or ultraviolet light. Illumination which emits visible light should satisfy a variety of requirements such as accurate color representation. One of these requirements is little flickering. Since humans cannot perceive 200 or more flickers per second, illumination apparatuses using Light Emitting Diodes (LEDs) having fast flicker performance control flickering using Pulse Width Modulation (PWM) in order to increase the lifespan thereof and save energy.
VLC is a wireless communication technology using a wavelength in the visible range from 380 to 780 nm. Although VLC is similar to infrared communication, they are different in the wavelength range used. Communication technology using light in the communication range includes Infrared Data Association (IrDA) using the infrared range, VLC using visible light, and optical communication using optical fiber.
Although the Infrared Data Association (IrDA) is a nongovernmental standard organization that was found in 1993 to establish standards for infrared data communications, IrDA also refers to the communication standards established by the IrDA. Principal standards for PC personal computers include IrDA1.0 for a maximum data transmission speed ranging from 2.4 to 115.2 kbps and IrDA1.1 for maximum data transmission speeds of 1.152 Mbps and 4 Mbps. IrDA is technology for performing communication using a wavelength in the infrared range from 850 to 900 nm.
VLC is a wireless communication technology using a wavelength in the range of 380 nm to 780 nm. The visible light communication standardization process is being conducted within the IEEE 802.15 Wireless Personal Area Network (WPAN) Working Group. In Korea, the Telecommunications Technology Association (TTA) is operating a visible light communication working group.
In general, a method of determining a location of a receiving terminal using VLC is based on a method of transferring different identifications (IDs) for respective illumination lights, as illustrated in FIG. 1, and determines that a receiving terminal is placed at a location where an illumination light is placed when an identification (ID) transmitted by the corresponding illumination light is received.
For example, U.S. Patent Application Publication No. 2012-0154824 entitled “Position Measuring Apparatus and Method” discloses a technology for measuring a position based on information provided by at least one communication device including a transmission light source.
Although technology for determining the location of a terminal using VLC has been actively researched as described above, there is still a need for a technology for determining the location of a terminal more accurately than a technology for receiving location information from a plurality of illumination lights.